Plasma processing apparatus, protecting layer therefor and installation of protecting layer

ABSTRACT

The following plasma processing apparatus can suppress the production of contaminants from the plasma processing chamber of the apparatus and an article in the plasma processing chamber which are allowed to act as ground electrodes: a plasma processing apparatus in which a workpiece is processed by creating a plasma in the processing chamber, and one or more surfaces made of a grounded metal electric conductor which come into contact with the plasma in the plasma processing chamber are coated with a plasma-resistant polymeric material having a relationship between relative dielectric constant k∈ and thickness t (μm) of t/k∈&lt;300, or a protecting layer formed of a plasma-resistant and water-absorbing resin material is adhered and fixed to the outer surface of an article in the processing chamber by its swelling and then shrinkage.

This application is a Divisional application of prior application Ser.No. 10/083,546, filed Feb. 27, 2002, now abandoned the contents of whichare incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

This invention relates to a plasma processing apparatus for processing aworkpiece by applying a high-frequency bias voltage to the workpiece byuse of a plasma, a protecting layer for plasma processing apparatusprovided in the processing chamber of the plasma processing apparatus,and a method for installing the protecting layer.

Apparatus such as that disclosed in JP-A-2001-57361 have been known as aplasma processing apparatus for processing a workpiece by applying ahigh-frequency bias voltage to the workpiece by use of a plasma. Theapparatus disclosed in the above reference is as follows.

An antenna capable of emitting electromagnetic waves is provided in theupper part of a plasma processing chamber. A bottom electrode forsetting a wafer thereon as a workpiece is provided in the lower part ofthe plasma processing chamber. A processing gas introduced into theplasma processing chamber is made into plasma by the interaction betweenelectromagnetic waves emitted by the antenna and a magnetic fieldcreated by a magnetic-field-creating means. A wafer is subjected toetching treatment by controlling ions and radicals in the plasma byadjusting a bias electric power applied to the antenna and a biaselectric power applied to the bottom electrode. For the etchingtreatment, a mixed gas containing a fluorocarbon type gas is used as thetreating gas. Thus, a silicon dioxide film is etched.

A 2-mm thick sidewall sleeve composed of a resin layer of a polyetherimide or the like is provided on the inner wall of the plasma processingchamber so as to be removable. Thus, contamination with a metal from ametal wall surface constituting the plasma treating chamber isprevented, and carbon-containing deposits are stably accumulated on theresin layer to suppress the production of contaminants.

As another prior art using a resin in order to prevent thecontamination, that disclosed in the specification of U.S. Pat. No.4,397,724 (JP-B-4-62170) can be exemplified. This reference disclosesthat a wafer is subjected to etching treatment after being mounted in areactor at least some of the inner surfaces of which have been coatedwith a polyarylate polymer, and that a thickness of the coating of aboutone-sixteenth inch is advantageous.

BRIEF SUMMARY OF THE INVENTION

A first object of the present invention is to provide a plasmaprocessing apparatus that permits easy replacement of a layer forprotecting the outer surface of an article in the processing chamber ofthe apparatus.

A second object of the present invention is to provide a protectinglayer for plasma processing apparatus that can easily be attached to theouter surface of an article in the processing chamber of a plasmaprocessing apparatus.

A third object of the present invention is to provide a method forinstalling a protecting layer for plasma processing apparatus whichpermits easy attachment of the protecting layer to the outer surface ofan article in the processing chamber of a plasma processing apparatus.

A fourth object of the present invention is to provide a plasmaprocessing apparatus which permits protection of the outer surface of anarticle in the processing chamber of the apparatus without lessening theeffect of the article in the processing chamber as an electrical groundfor plasma.

A fifth object of the present invention is to provide a plasmaprocessing apparatus which prevents contamination with a metal from aplasma processing chamber functioning as an electrical ground, andpermits easy control of the temperatures of one or more surfaces exposedto a plasma in the processing chamber.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view showing a plasma etchingapparatus as one example of the plasma processing apparatus of thepresent invention.

FIG. 2 is a vertical cross-sectional view showing the details of thebottom electrode portion of the apparatus shown in FIG. 1 and portionsaround the bottom electrode.

FIG. 3A and FIG. 3B are perspective cross-sectional views of abottom-electrode cover and a cylindrical liner, respectively.

FIG. 4 is a flow chart showing a method for attaching the cylindricalliner to the bottom-electrode cover of the apparatus shown in FIG. 2.

FIG. 5 is a perspective cross-sectional view showing a combination ofthe bottom-electrode cover and cylindrical liner of the apparatus shownin FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

In a plasma etching apparatus, the production of contaminants in aprocessing chamber by plasma irradiation should be suppressed. In orderto suppress the production of contaminants, a protecting layer is formedon each of the inner wall surface of the processing chamber and thesurface of an article in the processing chamber. On the inner wallsurface of the processing chamber, the production of contaminants can besuppressed by providing a sidewall sleeve (a cylindrical liner) made ofa resin such as a polyether imide, on the inner wall surface as in theformer prior art (JP-A-2001-57361) described above. On the surface ofthe article in the processing chamber, a plasma-resistant coating filmis generally formed. The plasma-resistance coating film is formed bymodification into a plasma-resistant material, such as anodizedaluminum, or coating with a plasma-resistant polymeric material.

In the former prior art (JP-A-57361), the attachment of a resin layer (aprotecting layer) to the inner wall surface of the processing chamber istaken into consideration, but grounding for plasma and the attachment ofa resin layer to the surface of an article in the treating chamber arenot sufficiently taken into consideration.

A high-frequency bias electric power should be applied to a bottomelectrode in a process in which the introduction of high-energy ions isindispensable, such as etching of silicon dioxide film. On the otherhand, in an apparatus in which the creation of a plasma and energy forthe introduction of ions in the plasma into a wafer are independentlycontrolled [e.g. an apparatus having in its plasma processing chamber anantenna capable of emitting electromagnetic waves of a high-frequencyelectric power, such as the antenna described above, and a bottomelectrode which faces the antenna and to which a bias voltage isapplied; or an apparatus having in its plasma processing chamber a topelectrode to which a high-frequency electric power is supplied and abottom electrode which faces the top electrode and to which a biasvoltage is applied], the antenna or top electrode which faces the bottomelectrode functions as a ground electrode with respect to ahigh-frequency electric power for bias applied to the bottom electrode.However, also in an apparatus having such a structure, the inner wallsurface of the electrically grounded plasma processing chamber is etchedby a plasma. This fact indicates that the antenna or top electrode whichfaces the bottom electrode does not function as a perfect electricalground for high-frequency electric power. The fact also indicates that asheath is formed between electrically grounded plasma processing chamberand the plasma, so that the plasma processing chamber also functions asan ground electrode for high-frequency electric power.

However, in the former prior art, the sidewall sleeve provided on theinner wall surface of the processing chamber is as thick as 2 mm.Therefore, the sidewall sleeve becomes a resistor between the processingchamber and a plasma to a high-frequency electric power, so that theprocessing chamber becomes ineffective as a ground electrode. As aresult, the surface of the sidewall sleeve is covered with depositscomposed of the components of a processing gas used in a plasma process,resulting in causing a problem of production of contaminants by thedeposits.

In the former prior art, the outside diameter of the sidewall sleeve ismade smaller than the inside diameter of inner wall of the processingchamber by about 0.1 mm to facilitate the installation of sidewallsleeve in the processing chamber. During plasma processing, the sidewallsleeve is swollen by heat introduced from a plasma, to adhere to theinner wall of the processing chamber. Thus, the conduction of heatbetween the sidewall sleeve and the inner wall of the processing chamberis improved. Such a sidewall sleeve, however, cannot be used on theouter surface of an article such as that in the processing chamberbecause it is thermally swollen during plasma processing.

On the other hand, in the method in which a plasma-resistant coatingfilm is formed on the surface of an article in the processing chamber,the coating film is consumed by the sputtering action of ions from aplasma, so that the time of maintenance of the inhibitory effect oncontaminants is determined by the thickness of the coating film. Inaddition, the thickness of the coating film is limited by a method forforming the coating film and hence cannot be increased without alimitation. If the coating film is consumed by repeated plasmaprocessing operations, the coating film should be reformed. In suchmaintenance, the timing of reformation of the coating film and the costof the reformation are important. Moreover, depending on the thicknessof the coating film formed, the coating film becomes a resistor betweena plasma and an article in the grounded processing chamber to lessen theeffect of the article as an electrical ground.

Also in the latter prior art (the specification of U.S. Pat. No.4,397,724 (JP-B-4-62170)) described above, an electrical ground forplasma is not sufficiently taken into consideration. When the inner wallof a plasma processing chamber is coated with-a polyarylate polymerlayer of about one-sixteenth inch in thickness as in the latter priorart, the inner wall does not function as an electrical ground forplasma. Therefore, a plasma diffuses in search of an electrical ground,so that it is used for etching as a low-density plasma. Moreover, sincethe ground potential is not determined, a plasma created in the plasmaprocessing chamber diffuses, so that the plasma density on a wafer to besubjected to etching process is decreased. Accordingly, the etching rateof the wafer is decreased.

The present invention was made in order to solve the problems in theabove prior arts.

The above first object of the present invention can be achieved asfollow: in a plasma processing apparatus in which a workpiece is treatedby creating a plasma in a processing chamber, a protecting layer formedof a plasma-resistant and water-absorbing resin material is adhered andfixed to the outer surface of an article in the processing chamber byits swelling and then shrinkage to prevent electrical insulation of theplasma and the article from each other.

The above second object can be achieved by forming a protecting layer onthe outer surface of an article in the processing chamber of a plasmaprocessing apparatus as follows: the protecting layer is formed of aplasma-resistant and water-absorbing resin material so as to have such ashape that the protecting layer becomes larger than the external shapeof the article in the processing chamber when it absorbs water.

The above third object can be achieved as follows: in a method forinstalling a protecting layer to be provided on the outer surface of anarticle in the processing chamber of a plasma processing apparatus, theprotecting layer is formed of a plasma-resistant and water-absorbingresin material and allowed to absorb water to be swollen, and thearticle in the processing chamber is inserted into the protecting layer,after which water is evaporated from the protecting layer by heating toshrink the protecting layer, whereby the protecting layer is fixed tothe article in the processing chamber.

In addition, the above third object can be achieved as follows: in amethod for installing a protecting layer to be provided on the outersurface of an article in the processing chamber of a plasma processingapparatus, said protecting layer is formed of a plasma-resistant andwater-absorbing resin material and allowed to absorb water to beswollen, and the article in the processing chamber is inserted into theprotecting layer, after which water contained in said protecting layeris evaporated while keeping said protecting layer at a pressure lowerthan atmospheric pressure, to shrink the protecting layer, whereby theprotecting layer is fixed to said article.

The above fourth object can be achieved as follows: in a plasmaprocessing apparatus in which a workpiece is processed by creating aplasma in a processing chamber, a protecting layer formed of aplasma-resistant and water-absorbing resin material comprising apolymeric material having a relationship between relative dielectricconstant k∈ and thickness t (μm) of t/k∈<300 is adhered and fixed to theouter surface of an article in the processing chamber by its swellingand then shrinkage to prevent electrical insulation of the plasma andthe article from each other.

The above fifth object can be achieved as follows: in a plasmaprocessing apparatus in which the creation of a plasma and the controlof energy for the introduction of ions into a workpiece areindependently carried out, one or more surfaces made of a grounded metalelectric conductor which come into contact with the plasma in a plasmaprocessing chamber are coated with a plasma-resistant polymeric materialhaving a relationship between relative dielectric constant kε andthickness t (μm) of t/k∈<300.

The plasma-resistant polymeric material is formed into a cylindricalliner whose outside diameter is larger than the inside diameter of theplasma processing chamber.

Silicone resin is located on the periphery surface of the cylindricalliner, and the cylindrical liner is closely attached to the innersurface of the plasma processing chamber through the silicone resin.

Alternatively, the plasma-resistant polymeric material is formed on theinner surface of the plasma processing chamber by spraying or coating.

Another embodiment is as follows: in a plasma processing apparatus foroxide film in which the creation of a plasma and the control of energyfor the introduction of ions into a workpiece are independently carriedout, the inner wall surface of a plasma processing chamber which is madeof a grounded metal electric conductor and in which the plasma iscreated is coated with a plasma-resistant polymeric material having arelationship between relative dielectric constant k∈ and thickness t(μm) of t/k∈<300.

Further another embodiment is as follows: in a plasma processingapparatus equipped with a plasma processing chamber in which at leastone surface to be exposed to plasma is made of a grounded metal; aplasma-creating means for creating a plasma with a plasma density of1×10³/cm³ (charged particles/cm³) or more in the plasma processingchamber; a workpiece holder provided in the plasma treating chamber inorder to set a workpiece thereon; and a high-frequency bias power sourceconnected to the workpiece holder and capable of giving an energysufficient to introduce ions in the plasma into the workpiece, the RFoutput of said high-frequency bias power source being 1 KW or more, theinner wall surface of metal portion of the plasma processing chamber iscoated with a plasma-resistant polymeric material having a groundingfunction with respect to the RF output.

Still another embodiment is as follows: in a plasma processing apparatusin which the creation of a plasma and the control of energy for theintroduction of ions into a workpiece are independently carried out, oneor more surfaces made of a grounded metal electric conductor which comeinto contact with the plasma in a plasma processing chamber are coatedwith a plasma-resistant polymeric material containing one or moreelectroconductive materials.

The protecting layer formed on the inner wall of a plasma processingchamber should have the following properties: it does not causecontamination of a wafer owing to plasma processing such as etching ordoes not scatter contaminants or the like on a wafer, and the processingchamber functions as a ground electrode for giving a reference potentialto a plasma. Therefore, as a material for the protecting layer, there isused a material which does not become a cause of the contamination or asource of contaminants, for example, a member made of a plasma-resistantpolymeric material composed of elements which constitute a gas used inan etching process and a material to be etched. In addition, a materialand a structure which have a low electrical resistance value are used sothat the plasma processing chamber may act as an electrical ground.

As a method for locating a plasma-resistant polymeric material on theinner wall surface of a plasma processing chamber, there are a method offorming the plasma-resistant polymeric material into a cylindrical linerhaving an outside diameter larger than the inside diameter of the plasmaprocessing chamber, and adhering and fixing the cylindrical liner to theinner wall surface of the plasma processing chamber by utilizing thetension of the material itself, and a method of providing the materialon the inner wall surface by spraying or applying the material on theinner wall surface. In both methods, a metal constituting the plasmaprocessing chamber, i.e., a vacuum chamber is not directly exposed to aplasma, so that the metal or the like is not scattered from the wall.Thus, floating contaminants are not deposited on the surface of a waferfor a semiconductor device and hence does not cause an undesirablewiring failure. Furthermore, since the plasma-resistant polymericmaterial is provided on the inner wall surface of the plasma processingchamber so as to adhere thereto closely, the conduction of heat from theinner wall of the plasma treating chamber is improved by temperaturecontrolling of the plasma processing chamber and the surface which comesinto contact with a plasma can be thermostated with good controllabilityeven in a narrow temperature range (temperature region), so that itbecomes possible to prevent the adhesion of deposits easily.

As to a protecting layer formed on the surface of an article to beexposed to a plasma in the plasma processing chamber, the timing ofreformation of the protecting layer and the cost of the reformation areimportant. Moreover, depending on the thickness of the protecting layerformed, the protecting layer becomes a resistor between a plasma and theprotected article to lessen the effect of the article as an electricallygrounded ground electrode. Therefore, it is effective to attach apolymeric material as plasma-resistant protecting member to the articlein the processing chamber in the form of a liner whose thickness can befreely set. The liner should be closely adhered to the periphery surfaceof the article so as not to get out of position, in order to protect thearticle against the plasma while allowing the article in the processingchamber to function as a ground electrode (i.e. as an electricalground), by utilizing the liner made of the plasma-resistant polymericmaterial. A method for attaching the liner is as follows. For example,when the periphery surface of a cylindrical article such as abottom-electrode cover is protected, a cylindrical liner having aninside diameter a little smaller than the outside diameter of thearticle is formed of a water-absorbing plasma-resistant material such asa polyimide at first. Then, the liner is allowed to absorb water and thearticle is inserted into the liner swollen by the water absorption. Theintegrated body of the cylindrical article and the liner is heated orplaced in a vacuum atmosphere, to evaporate the water contained in theliner and shrink the liner. Thus, the plasma-resistant liner can bestrongly fixed even to the article in the processing chamber, such asthe cylindrical article.

When a polymeric material (relative dielectric constant k∈ about 2.1 toabout 4.2) such as a polyamide-imide, polyether ether ketone, polyimide,polyether imide, polytetrafluoroethylene, polybenzoimidazole or the likeis used as a material for the plasma contact surface in the plasmaprocessing chamber, metals such as iron, chromium and nickel and metalcompounds such as aluminum fluoride are not released from the plasmacontact surface.

Furthermore, a grounding function can be imparted to the plasmaprocessing chamber by setting the thickness of the plasma-resistantpolymeric material attached to each of the inner wall surface of theplasma processing chamber and the periphery surface of an article in theprocessing chamber to a thickness smaller than a predeterminedthickness. In prior art, a plasma cover is located on the inner wall ofa plasma processing chamber and the thickness of the cover is specified,but physical property values of a material for the cover are not takeninto consideration. Whether the inner wall of the plasma processingchamber serves as an electrical ground for a plasma or not is determinedby the thickness and relative dielectric constant of the material, andit was found that the value of the relationship between relativedielectric constant k∈ and thickness t (μm) (t/k∈) is important. It wasalso found that the specification of values of the above relativedielectric constant k∈ and thickness t (μm) is important particularly inthe case of a polymeric material because the relative dielectricconstant changes depending on starting materials to be mixed, thesequence state and temperature.

It is also possible to allow a plasma-resistant material to function asan electrical ground for plasma, by incorporating one or moreelectroconductive materials such as silicon, carbon, etc. into theplasma-resistant material. In this case, a protecting layer for the wallcontains the electroconductive material(s) and acts as an electricalground, so that a plasma does not diffuse widely in the plasmaprocessing chamber. Since the silicon and/or carbon incorporated intothe plasma-resistant material is the same as in the case of an elementand a resist material, a wafer is not contaminated therewith.

Moreover, since a plasma-resistant material composed of theabove-exemplified polymeric material is composed mainly of elements suchas carbon, oxygen and hydrogen which are the same as the components of aresist, it has no undesirable influence on the processing of a wafer.

Thus, the amount of contaminants on a wafer to be subjected to plasmaprocessing and the degree of contamination of the wafer can be reduced,so that the fraction defective of the wafers subjected to plasmaprocessing can be reduced. Therefore, the productivity of the plasmaprocessing apparatus itself can be improved by locating theplasma-resistant material according to the present invention on theplasma contact surface in the plasma processing chamber of theapparatus.

Examples of the present invention are explained below with reference toFIGS. 1 to 5.

FIG. 1 shows a plasma etching apparatus to which the present inventionhas been applied. In detail, FIG. 1 shows an ECR type plasma etchingapparatus in which an antenna emits electromagnetic waves and a plasmais created by the interaction between the electromagnetic waves and amagnetic field. The temperature of the inner wall surface of a plasmaprocessing chamber, i.e., an etching chamber 1 in this case can beadjusted in a temperature range of 20 to 100° C. by a thermostatingmeans not shown. An antenna 3 is located in the upper part of theetching chamber 1 in this case through a dielectric 2. A high-frequencypower source 6 capable of generating UHF electromagnetic waves in thiscase is connected to the antenna 3 through a coaxial line 4 and amatching box 5. The dielectric 2 provided between the etching chamber 1and the antenna 3 can transmit electromagnetic waves. A magnetic-fieldcoil 7 for forming a magnetic field in the etching chamber 1 is providedaround the periphery of the etching chamber 1. A bottom electrode 10 asa workpiece holder for setting a wafer 9 thereon as a workpiece isprovided under the antenna 3 in the etching chamber 1. To the bottomelectrode 10 are connected a high-frequency bias power source 11 forgiving energy for introduction into the wafer 9 to ions in a plasma anda DC power source 12 for adsorbing the wafer 9 electrostatically on thebottom electrode 10. Numeral 8 denotes a gas feeder for feeding aprocessing gas into the etching chamber 1.

The etching chamber 1 is made of a metal and is grounded. The inner wallsurface of the etching chamber 1 is coated with a resin layer 14composed of a plasma-resistant polymeric material. In this case, theresin layer 14 is a 630-μm thick cylindrical liner made of apolytetrafluoroethylene. The outside diameter of the resin layer 14 ismade larger than the inside diameter of the etching chamber 1 by about0.2 to about 0.3 mm so that the resin layer 14 may be closely adhered tothe inner wall of the etching chamber 1 when set in the etching chamber1. In this case, the adhesion is further improved when the resin layer14 is set in the etching chamber 1 after locating flexible siliconeresin with a high thermal conductivity on the outer surface of the resinlayer 14 or thinly coating a silicone resin on outer surface of theresin layer 14. Thus, the difference between the temperatures of theresin layer 14 and the inner wall of the etching chamber 1 is narroweddown. The frequency of reformation of the resin layer 14 is preferablyreduced by increasing the thickness of the resin layer 14. Therefore, aplasma-resistant polymeric material having as high a relative dielectricconstant k∈ as possible is preferably used.

When the resin layer 14 is too thin to be formed into a cylindricalliner, the resin layer 14 can be formed in the etching chamber 1 bydissolving the resin in a solvent, spraying the resulting solution, andcontrolling the thickness of the resin layer 14 by adjusting, forexample, the number of spraying operations. In this case, the thermalconductivity is further improved because the resin layer is completelyadhered to the inner wall surface of the etching chamber 1.

When the resin layer 14 have a thickness of more than about 500 μm, itcan be formed into a cylindrical liner. When the resin layer 14 isformed by the spraying method, it can be formed in a thickness of uptoabout 500 μm. In addition, when the spraying method is adopted, theresin layer 14 can be formed in a thickness of about 800 μm or more byincorporating one or more electroconductive materials such as a silicon,carbon, etc. into the resin layer 14.

FIG. 2 is a detail view of the bottom electrode 10. A grounded electrodecover 104 is provided at the periphery of an electrode 101 through aninsulating material 102. A cylindrical liner 105, i.e., a cylindricalprotective member molded from a polyimide in this case is adhered andfixed to the periphery surface of the electrode cover 104. The purposeof grounding the electrode cover 104 is to prevent the diffusion of aplasma 13 caused when the plasma 13 misses the ground potential. Numeral103 denotes an insulating cover covering the periphery of the wafer 9 onthe electrode 101.

In the apparatus constructed in the manner described above, UHFelectromagnetic waves outputted from the high-frequency power source 6are supplied to the etching chamber 1 from the antenna 3 through thematching box 5, the coaxial line 4 and the dielectric 2. On the otherhand, a magnetic field is formed in the etching chamber 1 by thesolenoid coil 7 around the etching chamber 1. An etching gas introducedinto the etching chamber 1 is efficiently made into plasma by theinteraction of the electric field due to electromagnetic waves and themagnetic field due to the solenoid coil. Using this plasma 13, the wafer9 on the bottom electrode 10 is subjected to a predetermined etchingprocess. As the plasma used for such a process, a plasma having adensity of about 1×10¹⁰/cm³ or more is used. In the etching process,energy for the introduction of ions in the plasma into the wafer 9 isset so as to give a desirable etched shape, by controlling the energy byuse of the high-frequency bias power source 11. In a process requiring ahigh bias voltage, such as the etching process of an insulating filmtypified by a silicon dioxide film, the RF output from thehigh-frequency bias power source 11 should be 1 kW or more.

On the other hand, electric circuits are formed among an electricalground, the high-frequency bias power source 11, the bottom electrode10, the plasma 13 and the antenna 3 and between the etching chamber 1and an electrical ground, respectively. In this case, an ion sheath isformed also between the etching chamber 1 and the plasma 13, so thations in the plasma 13 are introduced into the inner wall of the etchingchamber 1. In the vicinity of the bottom electrode 10, an ion sheath isformed also between the grounded electrode cover 104 and the plasma 13,so that ions in the plasma 13 are introduced also into the outer wall ofthe electrode cover 104.

In this case, a grounding function can be imparted to theplasma-resistant protecting layer (the cylindrical liner 105) attachedto the surface of the electrode cover 104, in the plasma processingchamber (the etching chamber 1) by setting the thickness of theprotecting layer at a thickness not larger than a predeterminedthickness.

A sheath of plasma is present in the vicinity of the inner wall surfaceof the plasma processing chamber in which a plasma has been created andin the vicinity of the outer surface (the outer wall surface) of anarticle in the processing chamber. When the plasma is used for etching,the thickness of the sheath is determined by the plasma density. Theplasma density is determined by the composition of a gas used and an RFoutput employed. For example, when the density of the plasma created isabout 1×10¹⁰/cm³, the thickness of the sheath is about 600 μm. Therelative dielectric constant k∈ in the sheath is about 1.0, and thesheath resistance between the plasma and the wall can be considered tobe 600/1.0=600. When a resistor made of a resin or Alumilite is insertedbetween the sheath and the wall, it was experimentally found that thewall can be regarded as an electrical ground for the plasma even if sucha resistor having a resistance about one-half (about 300) as high as thesheath resistance is inserted.

Therefore, under conditions which satisfy the condition t/k∈<300 whereink∈ is the relative dielectric constant of the resistor inserted betweenthe sheath and the wall and t (mm) is the thickness of the resistor, thewall covered with the resistor acts as an electrical ground for theplasma. According to this fact, the thickness of the resistor can beabout 1065 μm or less when a polyimide resin (relative dielectricconstant: 3.55) is used as the resistor. The thickness of the resistorcan be about 630 μm or less when a polytetrafluoroethylene (relativedielectric constant: 2.1) is used as the resistor.

For example, when a silicon dioxide film is etched with a CF type gas(C₄F₈, C₅F₈ or the like), CxFy ions are produced in the plasma 13 andare drawn toward the etching chamber 1. In this case, the CxFy ions areintroduced into the resin layer 14 because the resin layer 14 isprovided on the inner wall surface of the etching chamber 1. Since theresin layer 14 of a polymeric material is composed of a CHF typecompound and hence has the same components as the ion components in theplasma, reaction products produced by the reaction of ions in the plasmawith the resin layer 14 and the components of the resin layer 14subjected to sputtering by the ions are also CF type compounds.Therefore, their undesirable influences on the etching process can beprevented. Thus, the resin layer 14 according to the present example iseffective in a process in which a CF type gas is used as a processinggas.

When the relative dielectric constant k∈ of the resin layer 14 is takenas 2.1, the thickness of the resin layer 14 having a relationship oft/k∈<300 is 630 μm. When the material according to the present example,i.e., a cylindrical liner of polytetrafluoroethylene is used, theetching chamber 1 can be allowed to act as an electrical ground.Therefore, the potential of the plasma 13 can be stabilized, so that adesirable etching process can be carried out by applying a necessarybias voltage to the wafer 9 by use of the high-frequency bias powersource 11.

In a process in which the application of a high bias voltage to thewafer 9 is unnecessary in etching process of a silicon dioxide film orthe like, the sheath voltage between the etching chamber 1 and theplasma 13 is low, so that the thickness of the resin layer 14 should bereduced.

FIG. 3A shows a schematic perspective section of the electrode cover104. FIG. 3B shows a schematic perspective section of the cylindricalliner 105 made of a polyimide which is a protecting layer. FIG. 4 showsa flow chart in the case of attaching the cylindrical liner 105 to theelectrode cover 104.

At first, the cylindrical liner 105 as a polyimide protective member forthe electrode cover 104 is formed so that its inside diameter may becomelarger than the outside diameter of the electrode cover 104 when thecylindrical liner 105 absorbs water to swell. That is, the insidediameter of the cylindrical liner 105 is set at a size a little smallerthan the outside diameter of the electrode cover 104 in view of theexpansion coefficient of the cylindrical liner 105 at the time of waterabsorption (shown in step 31 in FIG. 4). Although the thickness of thecylindrical liner 105 can be freely set, it should be set according tothe output of high-frequency electric power so that the cylindricalliner 105 may become an electrical ground for a high-frequency voltageapplied to the bottom electrode 10.

Then, the cylindrical liner 105 formed in the manner described above isallowed to absorb water by its immersion in a vessel containing purewater at ordinary temperature, to be swollen (shown in step 32 in FIG.4). In this case, the inside diameter of the cylindrical liner 105becomes a little larger than the outside diameter of the electrode cover104. Although pure water at ordinary temperature is absorbed above,employment of warm water is also effective. Or, in place of immersing inthe pure water tank, the pure water can be sprayed for water absorption,or there may be used in place of the pure water an alcohol or the like,which the liner absorbs to swell. Thereafter, as shown in FIG. 5, theelectrode cover 104 is inserted into the water-absorbed swelledcylindrical liner 105 (shown in step 33 in FIG. 4). Next, thecylindrical liner 105 having the electrode cover 104 inserted thereintois heated in a baking furnace to evaporate water and shrink the liner(shown in step 34 in FIG. 4). In this case, the heating temperature isset at a temperature that deteriorates neither the electrode cover 104nor the cylindrical liner 105. Owing to the shrinkage, the cylindricalliner 105 as a protective member is adhered and fixed to the electrodecover 104 (shown in step 35 in FIG. 4). As a method for evaporatingwater, there may be adopted a method of maintaining the cylindricalliner 105 having the electrode cover 104 inserted thereinto, at apressure lower than atmospheric pressure, or a combination of thismethod and heating may be employed.

As described above, according to the present example, the protectinglayer as a plasma-resistant protective member is adhered and fixed toeach of the inner wall surface of the plasma processing chamber and anarticle in the plasma processing chamber, whereby contamination withmetals from the inner wall surface and the article surface can beprevented. Moreover, by optimizing a material for covering the innerwall surface and the article surface and the thickness of the layer, agrounding function can be imparted to these surfaces.

In addition, in the present example, the plasma creation and the controlof energy for the introduction of ions into the wafer are independentlycarried out, so that a plasma having a necessary density can be stablycreated without any influence of the control of energy for theintroduction of ions. In such an etching processing apparatus, theetching chamber can be regarded as an electrical ground by coating thegrounded inner wall surface of the etching chamber with aplasma-resistant polymeric material having a relationship betweenrelative dielectric constant k∈ and thickness t (μm) of t/k∈<300, sothat a stable plasma potential can be given.

Although a polyimide is used as a material for the protective member ofplasma-resistant polymeric material in the example, there may be usedother plasma-resistant and water-absorbing polymeric materials such aspolyamide-imides, polyether ether ketones, polyether imides,polytetrafluoro-ethylenes, polybenzoimidazoles, etc.

According to the present example, in the case of etching a wafer into adesirable shape by applying a bias voltage obtained at a high-frequencyoutput of 1 kW or more to the bottom electrode which etching requires ahigh energy for the introduction of ions in a plasma into the wafer, thefollowing advantages can be obtained. Even if the inner wall surface ofthe etching chamber and an article in this processing chamber are etchedby their reaction and sputtering, contamination with metals from theetching chamber and the article in this processing chamber can beprevented because the inner wall surface of the etching chamber and thesurface of the article in this processing chamber are protected with theplasma-resistant polymeric material containing the same components asthose of a processing gas system. Moreover, the reaction products andsputtered layer produced by the inner wall surface have no undesirableinfluence on the process because they have the same components as thoseof the processing gas system. Thus, the fraction defective of waferssubjected to the etching process can be reduced, so that theproductivity of the etching apparatus can be improved. Furthermore,since the inner wall surface of the etching chamber 8 is coated with theplasma-resistant polymeric material, the heat of the thermostatedetching chamber is efficiently transmitted to the plasma-resistantpolymeric material, so that the temperatures of one or more surfaces tobe exposed to the plasma can easily be controlled.

According to the present example, a resin layer can be provided on theinner wall surface of the etching chamber so as to be closely adhered tothe inner wall surface. Therefore, the temperature of the inner surfaceof the resin layer can be equalized with the temperature of thethermostated etching chamber, and reaction products produced during theetching process of a silicon dioxide film can be prevented fromdepositing on the inner wall surface of the etching chamber, byadjusting the wall surface temperature of the etching chamber to about80° C. or higher.

According to the present example, the resin layer can be provided on theinner wall surface of the etching chamber so as to be closely adhered tothe inner wall surface. Therefore, the temperature of the inner surfaceof the resin layer can be equalized with the temperature of thethermostated etching chamber, and reaction products produced during theetching process of a silicon dioxide film can be deposited on the innerwall surface of the etching chamber so as to be strongly adhered to theinner wall surface, by adjusting the wall surface temperature of theetching chamber to about 40° C. or lower. Accordingly, peeling of theadhered deposits can be prevented, so that the adhesion of contaminantsderived from the reaction products to the wafer by their scattering canbe prevented.

According to the present example, the plasma-resistant polymerprotecting layer can easily be attached also to the outer surface of anarticle as in the case of the surface of an article in the etchingchamber by forming the protecting layer into a cylindrical liner andswelling the liner by water absorption. The liner can easily be closelyadhered to the article by evaporating (removing) water from the linerattached to the article.

Although a method for attaching the cylindrical liner to the cylindricalarticle is described in the present example, the present invention canbe conducted in the same manner as above not only in the case of acylindrical article but also in the case of an article having, forexample, a polygonal shape or the like.

In addition, although the plasma etching apparatus is described in thepresent example, an article in a processing chamber can be protected bythe same means as above also in other plasma processing apparatus.

When one or more electroconductive materials are incorporated into theplasma-resistant polymeric material, the resin layer itself tends to bethinned by a plasma. However, since the resin layer haselectroconductivity, a grounding function can be imparted to the resinlayer even when the thickness of the resin layer is increased. Moreover,the thickness of the resin layer can easily be increased. Therefore,such a resin layer is effectively used in an apparatus in which aprocess using a low bias voltage is employed.

The present example have the following other characteristics.

(1) A plasma processing apparatus for oxide film in which the creationof a plasma and the control of energy for the introduction of ions intoa workpiece are independently carried out, said apparatus beingcharacterized in that the inner wall surface of a plasma processingchamber which is made of a grounded metal electric conductor and inwhich the plasma is created is coated with a plasma-resistant polymericmaterial having a relationship between relative dielectric constant k∈and thickness t (μm) of t/k∈<300.

(2) A plasma processing apparatus equipped with a plasma processingchamber in which at least one surface to be exposed to plasma is made ofa grounded metal; a plasma-creating means for creating a plasma with aplasma density of 1×10¹⁰/cm³ or more in said plasma processing chamber;a workpiece holder provided in said plasma processing chamber in orderto set a workpiece thereon; and a high-frequency bias power sourceconnected to said workpiece holder and capable of giving an energysufficient to introduce ions in said plasma into said workpiece, the RFoutput of said high-frequency bias power source being 1 KW or more,which apparatus is characterized in that the inner wall surface of metalportion of said plasma processing chamber is coated with aplasma-resistant polymeric material having grounding function withrespect to said RF output.

(3) A plasma processing apparatus in which the creation of a plasma andthe control of energy for the introduction of ions into a workpiece areindependently carried out, said apparatus being characterized in thatone or more surfaces made of a grounded metal electric conductor whichcome into contact with said plasma in a plasma processing chamber arecoated with a plasma-resistant polymeric material containing one or moreelectroconductive materials.

According to the present invention described above, the following effectcan be obtained: a protecting layer member can easily be attached to theouter surface of an article in the processing chamber of a plasmaprocessing apparatus, so that the protecting layer can easily bereplaced.

According to the present invention, the following effect can also beobtained: there can be provided a method for attaching a protectinglayer for plasma processing apparatus which permits easy attachment ofthe protecting layer to the outer surface of an article in theprocessing chamber of a plasma processing apparatus.

In addition, according to the present invention, the following effectcan also be obtained: there can be provided a plasma processingapparatus which permits protection of the outer surface of an article inthe processing chamber of the apparatus without lessening the effect ofthe article in the processing chamber as an electrical ground forplasma.

Furthermore, according to the present invention, the inner surface of aplasma processing chamber can be made into an electrical ground forplasma by setting the thickness of a material covering the inner wallsurface of the plasma processing chamber and an article in theprocessing chamber at such a thickness that the relationship between therelative dielectric constant k∈ and thickness t (μm) of the material ist/k∈<300. It is also possible to prevent contamination with metals fromthe plasma processing chamber and an article in the processing chamberwhich are allowed to act as ground electrodes. The present invention hassuch an effect that a protecting layer can be installed so as to beclosely adhered and that the temperatures of one or more surfacesexposed to a plasma can easily be controlled.

It should be further understood by those skilled in the art that theforegoing description has been made on embodiments of the invention andthat various changes and modifications may be made in the inventionwithout departing from the spirit of the invention and scope of theappended claims.

1. In a method for installing a protecting layer for a plasma processingapparatus to be provided on the outer surface of an article in theprocessing chamber of a plasma processing apparatus, the improvementwherein said protecting layer is formed of a plasma-resistant andwater-absorbing resin material and allowed to absorb water to beswollen, and the article in the processing chamber is inserted into theprotecting layer, after which water is evaporated from said protectinglayer by heating to shrink said protecting layer, whereby the protectinglayer is fixed to said article, said article being an electrode cover,and said protecting layer being in a form of a cylindrical liner.
 2. Themethod according to claim 1, wherein said protecting layer has arelative dielectric constant in the range of about 2.1 to about 4.2. 3.The method according to claim 1, wherein said resin material is selectedfrom the group consisting of polyimide, polyamide-imide, polyether etherketone, polyether imide, polytetrafluoroethylene and polybenzoimidazole.4. The method according to claim 1, wherein, prior to being swollen, theprotecting layer has an inside diameter smaller than the outsidediameter of the electrode cover, and wherein after being swollen theinside diameter of the protecting layer is larger than the outsidediameter of the electrode cover.
 5. The method according to claim 1,wherein said protecting layer has a relative dielectric constant and athickness in μm such that a ratio of thickness to relative dielectricconstant is less than
 300. 6. In a method for installing a protectinglayer for a plasma processing apparatus to be provided on the outersurface of an article in the processing chamber of a plasma processingapparatus, the improvement wherein said protecting layer is formed of aplasma-resistant and water-absorbing resin material and allowed toabsorb water to be swollen, and the article in the processing chamber isinserted into the protecting layer, after which water contained in saidprotecting layer is evaporated while keeping said protecting layer at apressure lower than atmospheric pressure, to shrink the protectinglayer, whereby the protecting layer is fixed to said article, saidarticle being an electrode cover, and said protecting layer being in aform of a cylindrical liner.
 7. The method according to claim 2, whereinsaid protecting layer has a relative dielectric constant in the range ofabout 2.1 to about 4.2.
 8. The method according to claim 6, wherein saidresin material is selected from the group consisting of polyimide,polyamide-imide, polyether ether ketone, polyether imide,polytetrafluoroethylene and polybenzoimidazole.
 9. The method accordingto claim 6, wherein, prior to being swollen, the protecting layer has aninside diameter smaller than the outside diameter of the electrodecover, and wherein after being swollen the inside diameter of theprotecting layer is larger than the outside diameter of the electrodecover.
 10. The method according to claim 6, wherein said protectinglayer has a relative dielectric constant and a thickness in μm such thata ratio of thickness to relative dielectric constant is less than 300.